In the semiconductor fabrication, cleaning processes are required in pluralities of manufacturing steps to clean the silicon wafer. During the cleaning processes, various kinds of chemical liquids with different concentration and composition proportions are used. When the chemical liquids are mixed or used for a period of time, the original concentration will change, thus a certain amount of chemical liquids or ultrapure water are required to be replenished accordingly. Generally, the chemical liquids are stored in a chemical container, such as a tank or reservoir. At first, some chemical liquids with concentration satisfying the cleaning demand are fed into the container. These chemical liquids are reused during the cleaning processes which leads to the change of the chemical liquids concentration, and then additional chemical liquids or ultrapure water are required to be supplied. Consequently, there exists a need of replenishing chemical liquids or ultrapure water into the container periodically and quantitatively. Currently, the supplement of the chemical liquids or the ultrapure water are mostly determined by an electrically controlled metering pump utilizing signal control or signal feedback to achieve accurate supplement. However, such electrically controlled metering pump is quite large in size with complicated control system and structures, which increases the cost.